This invention is a method of correcting faults in the image produced by the detector in a detector camera and applies, in particular but not exclusively, to thermal cameras with an opto-mechanical scanning system.
When a scene is observed using a camera with series, parallel or series-parallel scanning, the image formed by the detector signals contains faults. For example, a uniform background observed by a camera does not give an uniform image at the camera output but an image whose signal may vary along a line and from one line to another and which can change, generally periodically, from the top to the bottom of the image.
To correct these faults, it has been proposed to subtract a memorized image, obtained by filming a uniform background, from the image of the scene formed by the detector signals.
The results obtained by this type of process are not always satisfactory. When looking for the reasons, inventors, supported by experimental evidence, have shown that the amplitude of the faults depends on the difference between the camera temperature and that of the scene observed. However, the uniform background used to produce the correction image memorized is not generally at the same temperature as the scene being observed by the detector; this is why the correction is generally unsatisfactory.